1. Technical Field
This invention relates generally to metachromatic measurement of heparin concentration, and more particularly to a new and improved method of assaying heparin in plasma with azure A.
2. Background Information
Heparin is an anticoagulant that is used in many applications such as in surgery of the heart and blood vessels, with organ transplants and artificial organs, for cardiovascular diagostic techniques, and for the control and prevention of thromboembolism following surgical operations. In this regard, it may be desirable to measure the heparin concentration in the patient in order to control the level of heparin and protamine (which is used to neutralize heparin). Failure to do so may result in a level that leads to hemorrhage and other clinical complications.
One method of colorimetric assay for plasma heparin propounded by M.D. Klein, et al. in a publication entitled "A colorimetric Assay for Chemical Heparin in Plasma", Analytical Biochemistry 1241, 59-64 (1982), employs the metachromasia of azure A when heparin is added. According to this method, heparin concentration is obtained from light absorbance measurements at a wavelength of six hundred twenty nanometers.
Although effective in some respects, it is found that measurements taken in this manner are inaccurate with diluted blood plasma, e.g. plasma containing saline. Thus, it is desirable to have a new and improved method that overcomes this concern while retaining the speed and simplicity of azure A assaying.